Which of the following numbers is NOT the square of a rational number?
A. 0.0016
B. 0.16
C. 1.6
D. 16
E. 1,600
The square root of 0.16 is 0.4, so 0.16 is a perfect square. The square root of 1,600 is 40, so 1,600 is a perfect square. The square root of 0.0016 is 0.04 so 0.0016 is a perfect square. Only 1.6 is not a perfect square.